JPH07185735A - Method for adjusting water content of molding sand - Google Patents

Abstract

PURPOSE:To stabilize the quality of castings and to improve the productivity over the entire part of a line by calculating primary feed water from a relation between the water content value retained by the charged sand and evaporated water content value, thereby increasing and decreasing the water content. CONSTITUTION:The recovered sand after knock-out of castings and some fresh sand are charged into a kneading machine and a fore stage is executed by adding the primary feed water of the molding sand to the mixture. The water content adjustment of the molding sand is executed by executing a next stage by repeating the second and subsequent water feeding in order to adjust the dissociation of the first measured compactability index CB1 and a target compactability index CB The primary feed water content W0 for the target value W1 of the primary water content set lower than the final target value water content W is, thereupon, calculated from the relation between the water content value W,, retained in the charged sand at the time of charging and the evaporated water content value W3 lost by the heat retrained before kneading which is experientially set and the heat generated during the kneading and is increased or decreased. As a result, the molding sand having stable characteristics are rapidly and smoothly supplied to the molding line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to adjusting the water content of a molding sand supplied to a molding site, particularly a molding sand for green molding.

[0002]

2. Description of the Related Art For molding sand for green molding, an appropriate amount of a binder such as bentonite is added to silica sand, water is added at an appropriate ratio to this, and the mixture is kneaded by a kneader and supplied to a molding site. It is well known that the proportion of the water content in the foundry sand has an important influence on the strength of the mold and the formability at the time of molding, and is listed as an important control item for the foundry sand. Especially for high-speed automatic molding lines, it is indispensable to supply stable molding sand without breaking the sand in order to maintain productivity.

It has not been particularly new to adopt the compactability index as a criterion for judging the formability of foundry sand, and it has been measured for a long time in a sand test room or the like at each foundry factory for daily management. . What is the compactability index? Casting sand is passed through a sieve (3 to 4 mm) into a container (100 mm height) of a predetermined size, and is tamped or pressed three times to determine the depth of sinking the height of the first container inside. It is the amount of compressive deformation expressed by% of the value divided by. It goes without saying that there is a deep causal relationship between this compactability index and the water content in the sand, but in recent years, the management of the foundry sand supplied to the molding line etc. by measuring this compactability index It has been proposed to develop a technique that will be implemented almost automatically.

A series of technical proposals are disclosed in Japanese Patent Publication No. 4-4055, Japanese Patent Publication No. 4-17743, and Japanese Patent Laid-Open No. 60-26.
As can be seen in Japanese Patent No. 1640, Japanese Patent Publication No. 4-
According to Japanese Patent No. 4055, a step of adding primary water to sand put into a kneader and a compactability index after this step are measured by physical means, and the first index which is the measured index value is measured. Based on the compactability index CB ₁ ,
The calculation of the amount of water required to obtain the target compactability index CB _P is performed using the calculating means based on the relationship curve between the compactability index and the amount of water having a substantially constant slope regardless of the amount of clay. The water content is adjusted in a subsequent step to obtain the target compactability index CB _P while further adding secondary water corresponding to the calculated water addition amount from the calculating means. According to this method, it is possible to systematize the line by automatic operation without being influenced by the increase / decrease of clay content in the foundry sand, and the recovered sand may contain some high temperature sand. .

[0005]

In the conventional technique in which the water content is adjusted by the compactability index, the compactability index CB ₁ is measured for the _first time after the primary water is supplied and kneading is performed for a predetermined time. Then, water is supplied based on the result calculated by the prepared program, the kneading is performed again for a predetermined time, and then the second compactability index CB ₂ is measured. If CB ₂ is within the range of CB _P , the kneading work can be finished here, but if this control target value is not reached, measurement-calculation-water supply must be repeated until it enters the range, Actually 1
It is rare to reach the end of kneading with a single correction, and it is not rare that the target is gradually approached by repeated trial and error. Since it is absolutely necessary for all functions in a casting plant to proceed in parallel, if the molding sand supplied to the casting machine is delayed, the entire line will stop and cause serious results. It is a requirement that only troubles that should not occur.

The most time-consuming factor in adjusting the compactability index is that the molding sand used in the foundry has special elements. Due to economic reasons and product quality, foundry sand is mainly composed of old sand that has been unmolded after casting, that is, recovered sand is the main component, and only a few percent of new silica sand is mixed into it to recover recovered sand. It compensates for aging and wear. Then, the recovered sand should be used for the next use after waiting for a long time after being unmolded, but in reality there is a limit to the capacity of the storage tank.
It is usually reused at a considerably high temperature without waiting for complete cooling. Moreover, the temperature of the recovered sand varies depending on the shape, volume and weight of the previous cast product and the time from casting to unmolding.Therefore, the temperature when actually input to the kneader is high and its degree. It is inevitable that there are various things.

Despite the large fluctuations in the temperature and residual water content of the recovered sand, the primary water supply amount is fixed and set as the basic value for management, so the first time after the end of the previous process It is self-evident that a large variation appears in the compactability index CB _1. Therefore, the range to be adjusted in the post-process of adjusting the secondary water supply must be extremely wide. In the prior art, the supplementary water supply amount is an arithmetic expression having a constant slope regardless of the amount of clay, so it is understood that the arithmetic operation is performed by a linear equation, but the coefficient of the linear equation itself is It is expected that large fluctuations will be required because it is not possible to keep up with fluctuations because it is processed with constants that have been averaged experimentally, although large fluctuations in the amount of heat possessed are expected.

In order to solve the above-mentioned problems, the present invention sets an appropriate primary moisture target value w ₁ according to the actual condition of the input sand at each time, and manages it by a few correction actions once or twice. The purpose of the present invention is to provide a method for adjusting the water content of foundry sand that reaches the limit.

[0009]

Means for Solving the Problems A method for adjusting the water content of foundry sand according to the present invention is a method in which the recovered sand after unmolding a cast product and a small amount of fresh sand are put into a kneader and before the primary water supply of the foundry sand is added. In the method of adjusting the water content of the casting sand, which comprises a step and a post-step of stacking secondary and subsequent water supplies to adjust the deviation between the _first compactability index CB ₁ and the target compactability index CB _P measured after the step, Loss of the primary water supply w ₀ for the primary water target value w ₁ set lower than the final target water value W due to the retained water value w ₂ of the input sand, the retained heat before kneading and the heat generated during kneading, which is empirically known. The above-mentioned problems have been solved by calculating from the relationship with the evaporation moisture value w ₃ which is obtained and increasing or decreasing.

[0010]

Since the final target moisture value W is formed by the primary moisture target value w ₁ and the corrected moisture value w ₄ , conversely, the corrected moisture value w ₄ is within the range completed by only one correction. If the primary moisture target value w ₁ can be set so as to stay at, the problem can be solved by obtaining the molding sand with the target properties by one correction. Primary moisture target value w ₁
In order to obtain the water content value of, the primary water content w ₀ actually added to the kneader is the water content value w ₂ remaining in the sand to be input, and the evaporative water value w _{3 that} can be empirically grasped from the temperature value before the addition. It suffices to add the element (newly to the calculation of w ₁ ) and perform the calculation.
Or primary water content w ₀ Add actually the kneader, the primary water supply amount w ₀ = primary water target value w ₁ - held water content w ₂ +
Evaporated water content w ₃ is calculated.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a systematic diagram of kneading related to an embodiment of the present invention, FIG. 2 is a flow incorporated for setting a primary moisture target value w ₁ , and FIG. 3 is a flow chart for controlling a compactability index. Is. As a system for supplying foundry sand, as shown in FIG. 1, the recovered sand recovered by demolding is temporarily stored in the recovered sand hopper 1 and is appropriately cut out by a signal from the sub hopper 3 to be appropriately extracted with a new sand from the new sand hopper 2 in the sub hopper. 3 is transported to the inside. The transported sand is transported to the load cell hopper 5 provided above the kneading machine 11, weighed (for example, 2300 Kg) and weighed into the kneading machine. Bentonite quantitatively measured from bentonite hopper 6 with a screw feeder (eg 10 kg)
After being cut out and stored in the bond hopper 7 above the kneading machine, it is put into the kneading machine.

On the conveyor 4 which conveys from the sub hopper 3 to the load cell hopper 5, the water content w ₂ of the input sand and the temperature of the sand at that time are measured and sent to the primary water supply controller 9 as shown in FIG. The primary water supply w ₀ is calculated. The detected temperature is empirically grasped empirically in advance and converted into an evaporated water content value w _{3 according} to an evaporated water content correction program stored in the controller, and is calculated together with other elements to obtain a primary water supply _value w _0, and the solenoid valve 13 is operated for a predetermined time. Open and supply water from the water supply tank 8 to the kneader. The kneaded sand which has been kneaded for a predetermined time is sent to the CB measuring device 12 to measure the first compactability index CB ₁ , and the result is sent to the CB controller 10 to determine the corrected water content w _{4 and} to turn the solenoid valve 13 again. Secondary water for correction is supplied from the open water tank.

Here, the final target moisture value W, the primary moisture target value w ₁ , the retained moisture value w ₂ , the evaporated moisture value w ₃ and the corrected moisture value w ₄ are all set in weight%, but the water supply amount is Since it is controlled by a transmission type flow meter, it is calculated in terms of volume (liters) inside the sequencer. Further, in setting the final target moisture value W, a large variation due to temperature change is inevitable in the evaporated moisture value w ₃ lost during transportation from the kneading machine to the molding machine in winter and summer, but this is controlled. This can be easily followed by adjusting the initial conditions of the device and inputting again, and since the setting of the primary moisture target value w ₁ is also performed by the counter, this change can be managed extremely easily on a daily basis. Further, by changing the setting while observing the transition of the CB value after the completion of the kneading, it is possible to absorb the error between the retained water value w ₂ and the evaporated water value w ₃ and pursue higher precision control.

For example, when adjusting molding sand having a kneading amount of 2300 Kg and a final target moisture value W of 4.36%,
The retained water value w ₂ of the recovered sand to be put into the kneader is 2.7%,
Assuming that the sand temperature is 41 ° C., the calculation proceeds in the following procedure. First, the primary moisture target value w ₁ is set and given by a counter, but it is empirically determined within a range in which the final target moisture value W can be adjusted by one correction, but in this embodiment, 4.
2% The primary water supply w ₀ added to the actual kneading machine in order to bring the water content after rough kneading to 4.2% is calculated by applying it to the formula. However, the primary moisture target value w ₁ and the retained moisture value w ₂
Is converted to the water content (liter) for the kneading amount of 2300 Kg. That is, w ₁ = 2300 × 0.042 = 96.6 liters w ₂ = 2300 × 0.027 = 62.1 liters, and the evaporation moisture value w ₃ is 7. 8 liters will be given. Therefore, the primary moisture supply w ₀ is w ₀ = 96.6-62.1 + 7.8 = 42.3 liters from the formula. The amount of water supply is controlled by a transmission type flow meter of 0.2 liters per pulse, so 42.3 liters of water supply is converted into a pulse signal of 212 pulses and sent to the sequencer of the solenoid valve,
The electromagnetic valve is opened and 212 × 0.2 = 42.4 liters of water is supplied to the kneader. After the rough kneading for 70 seconds, the moisture value is automatically confirmed and corrected by the compactability index according to the flow of FIG.

[0015]

The method for adjusting the water content of foundry sand according to the present invention comprises:
As described above, the primary water target value w ₁ is set so that it can always be adjusted by one subsequent correction, and the primary water supply amount is determined by incorporating all the fluctuations due to the previous process. The rationalization makes it possible to supply the molding line with stable and well-defined properties in a short time. After all, it is possible to prevent the trouble of waiting for sand and make a great contribution to the stability of the quality of cast products and the improvement of the productivity of the entire line.

[Brief description of drawings]

FIG. 1 is a system diagram of a molding sand kneading system according to an embodiment of the present invention.

FIG. 2 is a flow of the primary water supply system of the same example.

FIG. 3 is a flow of a CB controller of the same example.

[Explanation of symbols]

1 Collected sand hopper 2 Fresh sand hopper 3 Sub hopper 4 Conveyor 5 Load cell hopper 6 Bentonite hopper 7 Bond hopper 8 Water tank 9 Primary water supply control device 10 CB controller 11 Kneader 12 CB measuring device 13 Solenoid valve W Final target water content w ₀ Primary water supply w ₁ Primary moisture target value w ₂ Retained moisture value w ₃ Evaporated moisture value w ₄ Corrected moisture value CB ₁ First compactability index CB ₂ Second compactability index CB _p Target compactability index

Claims (1)

[Claims] 1. A pre-process in which the recovered sand after unmolding of a cast product and a small amount of fresh sand are put into a kneader and a primary water supply of the casting sand is added, and a first compactability index CB ₁ measured after the process. And the target compactibility index CB _P in order to adjust the deviation between the secondary and subsequent water supplies, in the method of adjusting the water content of the casting sand in the subsequent process, the primary water content value w ₁ set lower than the final water content value W is set. Increase / decrease by calculating the primary moisture supply w ₀ from the stored moisture value w ₂ of the input sand at the time of input, and the relationship between the retained heat before kneading and the evaporated moisture value w ₃ lost due to the heat generated during kneading, which is empirically determined A method for adjusting the water content of foundry sand, comprising: